Smoker's Lung: Pathology Photo Essay (cont.)

Michael C. Fishbein, MD

Dr. Fishbein received his undergraduate and medical degrees from the University of Illinois. He completed a residency in anatomic and clinical pathology at Harbor General Hospital/UCLA Medical Center. He is board certified in anatomic and clinical pathology.

Jay W. Marks, MD

Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

How does emphysema come about?

Simply put, the cigarette smoke attracts inflammatory cells (white blood cells, including neutrophils, lymphocytes, and macrophages) into the lung. Then, the inflammatory cells release substances called proteases. The proteases dissolve the proteins in the alveolar walls (septae) and thereby destroy the septae. As a result, the alveoli join together (coalesce) to form the larger, irregular, inefficient air sacs.

It turns out that about half of all smokers develop emphysema. Mild emphysema is seen occasionally in non-smokers and may be due to passive smoking (exposure to other people smoking, or "secondhand smoke") and industrial air pollution. Severe emphysema, however, is seen only in smokers or in some people with rare inherited diseases (e.g., alpha-1-antitrypsin deficiency). Still, it takes about 30 years of smoking to develop fatal emphysema. This is because people usually don't die from emphysema until more than 60% of the lung tissue is affected.

Why does smoker's lung look black?

The lung is connected and exposed by the airways to a potentially noxious outside world. Accordingly, the alveolar spaces normally contain specialized scavenger cells, called alveolar macrophages. The job of these macrophages is to engulf (phagocytize) any possibly harmful foreign material that enters the lung through the airways.

As you can imagine, cigarette smoke contains many impurities that are inhaled in great numbers directly into the lung. For this reason, the alveolar spaces of the smoker contain numerous scavenger cells (macrophages) that are filled with engulfed (phagocytized) particles of impurities and debris, as illustrated in

Picture of scavenger cells in a smoker's alveolus

Under the microscope, with this high magnification, you can actually see the black and brown engulfed particles in the alveolar scavenger cells. Indeed, smoker's lung may have so much of this particulate material that the lung looks gray-black to the naked eye.
Most of the time, you don't need a microscope to tell if someone is or was a heavy smoker. A naked eye examination of a smoker's lung will
usually reveal an enlarged gray-black lung with enlarged air spaces (the emphysema, as you saw in Figure 4 and will see again in Figure 8).